Karen's maximum sustained winds dropped to about 40 mph by midday Saturday. The storm was centered about 130 miles south-southwest of the Mississippi River's mouth about 10 p.m. CT (11 a.m. ET).

The mayor of Grand Isle, Louisiana, on Friday ordered a mandatory evacuation for the barrier island town, CNN affiliate WGNO-TV reported. Grand Isle has about 1,300 residents plus tourists. Mayor David Camardelle ordered them to take camper trailers and recreational vehicles off the island.

Karen moving toward Gulf Coast

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Shutdown won't impact storm response

A tropical storm warning is in effect from Morgan City, Louisiana, to the mouth of the Pearl River on the Louisiana-Mississippi line.

3 to 6 inches of rain

The storm is expected to drop 3 to 6 inches of rain over parts of the central and eastern Gulf Coast through Sunday night, mainly near and to the east of the storm's center, the hurricane center said. Isolated storm total amounts of 10 inches are possible.

Storm surges also are a concern. If peak surges coincide with high tide, water could reach 3 to 5 feet above ground from the mouth of the Mississippi River in Louisiana to Alabama's Mobile Bay, the center said.

"The combination of storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters," the center said.

The hurricane center's tracking map shows that the storm could make two landfalls: once over the Louisiana barrier islands Saturday night and again over the Florida Panhandle on Sunday morning.

Back to work at FEMA

The storm prompted the Federal Emergency Management Agency to recall some of its workers furloughed during the government shutdown. The agency also reactivated its Hurricane Liaison Team at the National Hurricane Center in Miami. FEMA officials in the Atlanta and Denton, Texas, offices are monitoring Karen.

"At all times, FEMA maintains commodities, including millions of liters of water, millions of meals and hundreds of thousands of blankets, strategically located at distribution centers throughout the United States, including in the Gulf Coast region, that are available to state and local partners if needed and requested," the agency said in a statement.

The hurricane center said it, too, would be unaffected by the government shutdown as Karen approaches.

"The National Hurricane Center is fully operational ... and has all of its resources available to it," spokesman Dennis Feltgen said in an e-mail. "The government shutdown will not inhibit NHC from providing its mission."

Storm preparations

Louisiana Gov. Bobby Jindal and Alabama Gov. Robert Bentley declared statewide states of emergency. Florida Gov. Rick Scott declared a state of emergency in 18 counties.